I totally agree markg... I've just finished a set of six bird quills made from very small pigeon feathers. They won't take much shotting as you say, but fished of the end of 14' rod and just lowered into the water (next to lilly pads for example.) they work well. Mine ranged from three to six inches long..
Some of the bigger feathers make very good lift floats if they are reversed. I've used Araldite Rapid to set a small ring into the thicker end and with a bit of whipping that is strong enough. The painted very fine 'thin' end sits very well in the water...
Regarding the natural curve of feathers; All bird feathers have a thick 'skin' down one side and opposite this a slightly thinner one. The opposing two sides are relatively soft and if a secondary curve is found here I have used an iron (with a cloth over the top) to inject some heat into the quill and then just lifted the float gently to bring it straight. With care this works well..
The natural main curve is more difficult to deal with IF you want to straighten it even slightly, as you are trying to straighten against the thick side which doesn't want to be straightened. I have tried bring one straight and all that happens is the thick side just creases and the resultant soft sides of the quill 'bulge' (the material has to go somewhere) and, well, it just doesn't work, at least not on large quills!
However, again with an iron, I have force straightened the bottom 50mm or so against the thick side (very thin so consequently far more flexible) to the point where this part of the float is parallel to the top, thicker end and this has the effect of making the quill 'straighter' and the curve slightly reduced - if you see what I mean!
In essence, none of this is absolutely necessary but to my mind the quill looks better and imho with the line closer to the remaining curve of the float it means it should offer less resistance, no matter how small, on the strike.
Of course, it is just as easy to take a quill of (say) 20cm long, trim off all the feathers, use a scalpel blade to remove most of the rough edges, give it a quick rub down to smooth the whole quill, add a touch of paint to the top 10cm and you have a pefectly good float in less than an hour!!
Just depends if you want a thing of beauty or something rough and ready that might only last a few sessions...................
ps I used to use a gas ring to straighten quills but the wife insisted we needed a new-fangled,more fashionable hob when we did up the kitchen, so my ring went to the dogs....Grrrrrrr